Post on 01-Jun-2018
8/9/2019 01 Wis5 Defect New
1/55
Welding InspectionDefects/Repairs
Course Reference WIS 5
8/9/2019 01 Wis5 Defect New
2/55
A perfect butt weld joint, when subjected to an external
force, provide a distribution of stress throughout itsvolume which is not significantly greater than parent
metal.
DefinitionDefinition
8/9/2019 01 Wis5 Defect New
3/55
DefinitionDefinition
This is achieved as long as the following featuresapply :-
• Welds should consists of solid metal throughout a cross
section at least equal to that of parent metal.• All parts of a weld should be fully fused to the parent
metal.
•Welds should have smoothly blended surfaces.
8/9/2019 01 Wis5 Defect New
4/55
Defects which may be detected by visual inspection can
be grouped under five headings
Cracs
!ac of solid metals
!ac of fusion
!ac of smoothly blended surfaces
"iscellaneous
#eld Defects#eld Defects
8/9/2019 01 Wis5 Defect New
5/55
CracsCracs
8/9/2019 01 Wis5 Defect New
6/55
Classified by Shape
!ongitudinal
$ransverse
%ranched
Chevron
Classified by Position
&A'
Centreline
Crater
(usion )one
*arent metal
CracsCracs
Cracs that may occur in welded materials are caused
generally by by many factors and may be classified byshape and position, cracs are classed as planar.
8/9/2019 01 Wis5 Defect New
7/55
*rocess Cracs*rocess Cracs
&A' hydrogen cracing
#eld metal hydrogen cracing
+olidification cracing &ot $earing-
!amellar tearing
8/9/2019 01 Wis5 Defect New
8/55
CracsCracs
HAZ hydrogen cracking Weld metal hydrogen cracking
Solidification cracking Lamellar Tearing
8/9/2019 01 Wis5 Defect New
9/55
Transverse crack Longitudinal crack
8/9/2019 01 Wis5 Defect New
10/55
8/9/2019 01 Wis5 Defect New
11/55
*R+$0*R+$0Description : Gas pores trapped within the weld metal
Causes
• !am" flu#es$ corroded electrode
•%rease$hydrocar&on$'ater
contamination of "re"ared surface
•Air entra"ment in gas shield
•Too high arc (oltage$arc length
•Incorrect$insufficient deo#idant
in electrode) filler or "arent metal
*re(ention
• +se dry electrodes in good
condition
•,"timise gas flo'
•+se electrode 'ith sufficient
deo#idation acti(ity
•Reduce arc (oltage or arc length
8/9/2019 01 Wis5 Defect New
12/55
1as Cavities1as Cavities
%oot piping%oot piping
&orosity&orosity
8/9/2019 01 Wis5 Defect New
13/55
Cluster porosity 'erring (one porosity
8/9/2019 01 Wis5 Defect New
14/55
Crater *ipeCrater *ipe A shrinkage cavity at the end of a weld run where the arc is
terminated
Causes
•Lack of 'elder skill due to using
"rocesses 'ith too high current-
•Ino"erati(e crater filler . %TAW /
*re(ention
• Retrain 'elder
•+se correct crater fillingtechni0ue
8/9/2019 01 Wis5 Defect New
15/55
Crater *ipe/CracsCrater *ipe/Cracs
Crater pipeCrater pipe
Crater CracksCrater Cracks
8/9/2019 01 Wis5 Defect New
16/55
RootRoot concavityconcavity
A shallow groove, which may occur in the root of a butt weld
Causes
•Insufficient arc "o'er to "roduce "ositi(e &ead
•1#cessi(e &acking "ressure . %TAW /
•Lack of 'elder skill
•Slag flooding in &acking &ar groo(e
*re(ention
• Raise arc energy
•Reduce gas "ressure
•Retraint 'elder
•Tilt 'ork to "re(ent slag
flooding
8/9/2019 01 Wis5 Defect New
17/55
root concavity
8/9/2019 01 Wis5 Defect New
18/55
2nderfill2nderfill
A weld with thickness less than that of the parent metal
Causes
•Insufficient 'eld metal
•Irregular 'eld &ead surface
*re(ention
• Increase num&er of 'eld run
•Retrain 'elder
8/9/2019 01 Wis5 Defect New
19/55
Inco)plete filled groove
8/9/2019 01 Wis5 Defect New
20/55
+lag nclusions+lag nclusions
Slag or other matters trapped during welding. The imperfection is of
an irregular shape and thus differs in appearance from a gas pore
Causes
•Hea(y millscale$rust on 'ork surface
•Incom"lete slag remo(al from
underlying surface of multi"ass 'eld
•Slag flooding ahead of the arc
•1ntra"ment of slag in 'ork surface
•+nfused flu# due to damage coating
*re(ention
• %rind surface "rior 'elding
•Im"ro(e interun slag remo(al
•*osition 'ork to gain control of
slag
•!ress 'ork surface smooth
•+se electrode in good condition
8/9/2019 01 Wis5 Defect New
21/55
$longated slag linesInterpass slag inclusions
8/9/2019 01 Wis5 Defect New
22/55
nter3 run mperfectionsnter3 run mperfections
Irregular along the fusion line between weld beads
Causes
•Lo' arc current resulting in lo'
fluidity of 'eld "ool
•Too high tra(el s"eed
•Inaccurate &ead re"lacement
*re(ention
• Increase current
•Reduce tra(el s"eed
•Retrain 'elder
8/9/2019 01 Wis5 Defect New
23/55
!ac of (usion!ac of (usion
8/9/2019 01 Wis5 Defect New
24/55
ncomplete root penetrationncomplete root penetration
Failure of the weld metal to extend into root of a oint
Causes
•1#cessi(ely thick root face) insufficient root ga"
or failure to cut &ack sound metal in a 2&ack
gouging3 o"eration
•Lo' heat in"ut
•1#cessi(e inductance in %4AW di" transfer
•S4AW electrode too large. lo' current density /
•+se of (ertical do'n 'elding
*re(ention
• Im"ro(ed &ack gouging and edge
"re"aration
•Increase arc "o'er or decrease tra(els"eed
•Im"ro(e electrical settings and "ossi&ly
s'itch to s"ray transfer
•Reduce electrode sie
•S'itch to (ertical u" "rocedure
8/9/2019 01 Wis5 Defect New
25/55
Root DefectsRoot Defects
Lack of root fusion Lack of root &enetration
8/9/2019 01 Wis5 Defect New
26/55
8/9/2019 01 Wis5 Defect New
27/55
!ac of sidewall fusion!ac of sidewall fusion
!ack of fusion between weld metal and parent metal at one side of weld
Causes
•Lo' heat in"ut to 'eld
•4olten metal flo'ing ahead of arc
•,#ide or scale on 'eld "re"aration
•1#cessi(e inductance in %4AW di" transfer
'elding
*re(ention
•Increase arc energy or increase tra(el
s"eed
•Im"ro(e electrode angle and 'ork
"osition
•Im"ro(e edge "re"aration "rocedure
•Reduce inductance) e(en if this increase
s"atter
8/9/2019 01 Wis5 Defect New
28/55
!ac of +moothly!ac of +moothly
%lended +urfaces%lended +urfaces
8/9/2019 01 Wis5 Defect New
29/55
+urface porosity+urface porosity
"as pores which break the surface of the weld
Causes
•!am" or contaminated surface of electrode
•Lo' flu#ing acti(ity
•1#cess sul"hur . "articularly free 6 cutting steels/
"roducing sul"hur o#ide
•Loss of gas shield gas due to long arc or high
&reees . %4AW /
*re(ention
•Clean surface and dry electrodes
•+se a high acti(ity flu#
•+se high manganese to "roduce 4nS)
note free cutting should not normally &e
'elded
•Reduce arc length
8/9/2019 01 Wis5 Defect New
30/55
4xcess #eld "etal Reinforcement -4xcess #eld "etal Reinforcement -
#einforcement is the extra metal which produces convexity in fillet
welds and a welds thickness than the parent metal plate in butt welds.
Causes
•1#cess arc energy . %4AW)SAW /
•Shallo' edge "re"aration
•7aulty electrode mani"ulation
•Incorrect electrode sie
*re(ention
•Reduction of energy in"ut
•!ee"en edge "re"aration
•Im"ro(e 'elder skill
•Reduce electrode sie
8/9/2019 01 Wis5 Defect New
31/55
$*cess cap reinforce)ent
8/9/2019 01 Wis5 Defect New
32/55
4xcessive *enetration4xcessive *enetration
$roection of the root penetration bead beyond a specified limit
Causes
•Weld in"ut energy too high
•Incorrect 'eld "re"aration i-e e#cessi(e
root ga") thin edge "re"aration) lack of
&acking
•+se electrode unsuited to 'elding "osition
•Lack of 'elder skill
*re(ention
•Reduce arc "o'er$increase 'eld s"eed
•Im"ro(e 'ork "iece "re"aration
•+se correct electrode "osition
•Retrain 'elder
8/9/2019 01 Wis5 Defect New
33/55
$*cessive root penetration
8/9/2019 01 Wis5 Defect New
34/55
2ndercut2ndercut
An irregular groove at the toe of a run in the parent metal or in
previously deposited welding, cause by welding
Causes
•4elting of to" edge due too high 'elding
current . es"ecially at free edge/ or high
tra(el s"eed•Attem"ting an H8 fillet 'eld leg length
9:-; 44
• 1#cessi(e$Incorrect 'ea(ing
•Incorrect electrode angle
*re(ention
•Reduce "o'er in"ut) es"ecially
a""roaching a free edge 'here o(erheatingcan occur
•Weld in a flat "osition or use multirun
techni0ue
•!irect arc to'ards thicker mem&er
C 2 d t
8/9/2019 01 Wis5 Defect New
35/55
Cap 2ndercutCap 2ndercut
"easured in both !ength 5 Depth"easured in both !ength 5 Depth
8/9/2019 01 Wis5 Defect New
36/55
Cap undercut%oot undercut
8/9/2019 01 Wis5 Defect New
37/55
verlapverlap
An Imperfection at the toe of a weld caused by metal flowing on to the
surface of the parent metal without fusing to it
Causes
• *oor electrode mani"ulation
• High energy in"ut$lo' tra(el s"eed
causing surface flo' of fillet 'eld
• Incorrect "ositioning of 'eld
• 1lectrode ha(ing too high a fluidity
*re(ention
•Retrain 'elder
•Reduce the heat in"ut or limit sie of
fillet 'eld to :-; mm leg &y using multi
run 'eld
•Change the flat "osition
•Change to less fluid 'eld metal
8/9/2019 01 Wis5 Defect New
38/55
*rofile Defects*rofile Defects
&oor stop+starts
8/9/2019 01 Wis5 Defect New
39/55
"iscellaneous"iscellaneous
8/9/2019 01 Wis5 Defect New
40/55
"isalignment"isalignment
The non % alignment of two abutting edges in a butt oint
Causes
• Inaccuracies in assem&ly "rocedures or
distortion from other 'elds
• 1#cessi(e 2out of flatness< in hot rolled
"late or sections
*re(ention
•Ade0uate checking of alignment "rior to
'elding cou"led 'ith the use of clam"sand 'edges
•Check accuracy of rolled section "rior to
'elding
8/9/2019 01 Wis5 Defect New
41/55
Arc stries Arc stries#andom areas of fused metal where the electrode, the holder, or
current return clamp accidentally touched the work and produced a
short duration arc
Causes
• *oor Access to 'ork
• 4issing insulation on electrode holderor torch
• 7ailure to "ro(ide an insulated resting
"lace for the electrode holder or torch
'hen not in use
• Loose current return clam"
*re(ention
•Im"ro(e access . modify assem&ly
se0uence /
•Institute a regular ins"ection scheme for
electrode holders and torches
•*ro(ide an insulated resting "lace
•Regularly maintain current return clam"
+
8/9/2019 01 Wis5 Defect New
42/55
+patter +patter
Small droplets of electrode material can be proected clear of the weld
and may fused to the parent metal
Causes
• High arc "o'er
• 4agnetic arc &lo'
• Incorrect setting for %4AW "rocess
• !am" electrodes
*re(ention
•Reduce arc "o'er
•Reduce arc length or s'ith to AC "o'er
•4odify electrical settings . &ut &e careful
to maintain full fusion
•+se dry electrodes
% $h h% $h h
8/9/2019 01 Wis5 Defect New
43/55
%urn $hrough%urn $hrough
&igh Amps/volts
+mall Root face
!arge Root 1ap
+low $ravel +peed
%urn through
A locali&ed collapse of the weld pool due to excessive
penetration resulting in a hole in the root run
R t D f t
8/9/2019 01 Wis5 Defect New
44/55
,urn through
,urn
Through
Root Defects
R t C i / idi d R tR t C i / idi d R t
8/9/2019 01 Wis5 Defect New
45/55
Root Coing/xidi)ed RootRoot Coing/xidi)ed Root
!oss or insufficient bac
purging gas
"ost commonly occurs
when welding stainlesssteels
*urging gases include
argon, helium andoccasionally nitrogen
8/9/2019 01 Wis5 Defect New
46/55
"echanical Damage"echanical Damage
"echanical Damage"echanical Damage
8/9/2019 01 Wis5 Defect New
47/55
"echanical Damage"echanical Damage
"echanical damage can be defined as any surface material
damage cause during the manufacturing process.$his can included damage caused by6
1rinding
&ammering
Chiselling
Chipping
%reaing off welded attachments torn surfaces-
2sing needle guns to compress weld capping runs
* t " t i l D f t* t " t i l D f t
8/9/2019 01 Wis5 Defect New
48/55
*arent "aterial Defects*arent "aterial Defects
A welding inspector should also inspect the parent
material for any visible defects
!amination
"echanical damage !ap
+egregation line
*l t ! i ti*l t ! i ti
8/9/2019 01 Wis5 Defect New
49/55
*late !amination*late !amination
8/9/2019 01 Wis5 Defect New
50/55
Any uestions.Any uestions.
7 ti7uestions
8/9/2019 01 Wis5 Defect New
51/55
7uestions7uestions
72 8. 1ive two main causes for the occurrence of a burn through
72 9. 1ive two main causes for the occurrence of excessive rootpenetration on a single3: butt weld
72 ;. 1ive five defects, which may occur when welding carbon
steel using the ""A welding process with the current settingto low
72
8/9/2019 01 Wis5 Defect New
52/55
#eld Repairs#eld Repairs
#elding Repairs#elding Repairs
8/9/2019 01 Wis5 Defect New
53/55
#elding Repairs#elding Repairs
Authori)ation for repair
Removal and preparation for repair
$esting of repair 3 visual and >D$
n the event of repair
#eld Repairs#eld Repairs
8/9/2019 01 Wis5 Defect New
54/55
A weld repair may be used to improve weld profiles or
extensive metal removal Repairs to fabrication defects are generally easier than
repairs to service failures because the repair procedure
may be followed
$he main problem with repairing a weld is the
maintenance of mechanical properties
During the inspection of the removed area prior to welding
the inspector must ensure that the defects have been
totally removed and the original joint profile has been
maintained as close as possible
#eld Repairs#eld Repairs
#eld Repairs#eld Repairs
8/9/2019 01 Wis5 Defect New
55/55
$he specification or procedure will govern how the defective
areas are to be removed. $he method of removal may be
1rinding
Chipping
"achining
(iling
xy31as gouging
Arc air gouging
#eld Repairs#eld Repairs
Arc air gouging